NASAThe first mission to return a sample from an ancient asteroid arrived at its target, the asteroid Bennu, on December 3, 2018. This mission, Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer, or OSIRIS-REx, is a seven-year journey to be completed upon delivery to the ground of at least 2.1 ounces (60 grams) and possibly up to nearly four and a half pounds (two kg) of sample. It promises to be the largest amount of extraterrestrial material brought back from space since the Apollo era.
The 20th anniversary of the asteroid’s discovery was in September 2019 – and scientists have been collecting data ever since. Here’s what we already know (and some of what we hope to find out) about this pristine remnant from the early days of our solar system.
It’s very, very dark …
Bennu is classified as a B-type asteroid, which means that it contains a lot of carbon in and along with its various minerals. Bennus’ carbon content creates a surface on the asteroid that reflects about four percent of the light that hits it – and that’s not much. In contrast, the brightest planet in the solar system is Venus, reflects about 65 percent of incoming sunlight, and the Earth reflects about 30 percent. Bennu is a carbonaceous asteroid that has not undergone a drastic, composition-changing change, meaning that on and below its deeper-than-black surface there are chemicals and rocks from the birth of the solar system.
2.… And very, very old.
Bennu has been (mostly) undisturbed for billions of years. Not only is it conveniently dense and carbonaceous, it is also so primitive that scientists calculated it formed in the first 10 million years of the history of our solar system – over 4.5 billion years ago. Thanks to the Yarkovsky effect – the small push created when the asteroid absorbs sunlight and re-emits that energy as heat – and gravity towing from other celestial bodies, it has drifted closer and closer to Earth from its probable birthplace: the main asteroid belt between March and Jupiter.
3. Bennu is a “rubble” steroid – but do not let the name fool you.
Is Bennu space trash or scientific treasure? While “rubble” sounds like an insult, it is actually a true astronomy classification. Asteroids with rubble like Bennu are celestial bodies made up of lots of pieces of rock, which gravity compresses. This type of detritus is produced when a blow destroys a much larger body (for Bennu it was a parent asteroid about 60 miles away). [about 100 km] wide). Bennu, on the other hand, is about as tall as the Empire State Building. It probably only took a few weeks for these shards of space wreck to merge into the rubble that is Bennu. Bennu is full of holes inside where 20 to 40 percent of its volume is empty. The asteroid is actually in danger of flying apart if it begins to rotate much faster or interacts too closely with a planetary body.
4. Asteroids may have tips about the origin of all life on earth …
Bennu is an original artifact that is preserved in the vacuum of space and orbits planets and moons and asteroids and comets. Because it is so old, Bennu could have been made of material containing molecules that were present when life was first formed on Earth. All life forms on earth are based on chains of carbon atoms bonded with oxygen, hydrogen, nitrogen and other elements. However, organic material that the kind of scientists hope to find in a sample from Bennu does not necessarily always come from biology. However, it would further scientists’ search to uncover the role that asteroids rich in organic matter played in catalyzing life on Earth.
5. … but also platinum and gold!
Extraterrestrial jewelry sounds good, and Bennu is probably rich in platinum and gold compared to the average crust on earth. Although most are not made almost entirely of solid metal (but asteroid 16 Psyche can be!), Many asteroids contain elements that can be used industrially instead of Earth’s finite resources. Carefully studying this asteroid will provide answers to questions about whether asteroid extraction during deep space exploration and travel is possible. Although rare metals attract the most attention, water is probably the most important resource in Bennu. Water (two hydrogen atoms bonded to an oxygen atom) can be used for drinking or disassembled into its components to obtain breathable air and rocket fuel. Given the high cost of transporting material into space whose astronauts can draw water out of an asteroid for life support and fuel, the cosmic is beyond ever closer to being humanly accessible.
6. Sunlight can change the entire orbit of the asteroid.
Gravity is not the only factor involved in Bennus’ fate. The side of Bennu facing the sun is heated by sunlight, but a day on Bennu lasts only 4 hours and 17.8 minutes, so the part of the surface facing the sun is constantly changing. As Bennu continues to rotate, it expels this heat, giving the asteroid a slight push toward the sun by approx. 0.18 miles (approximately 0.29 kilometers) per year and changes its trajectory.
7. There is a small chance that Bennu will affect the earth late in the next century.
The NASA-funded Lincoln Near-Earth Asteroid Research team discovered Bennu in 1999. NASA’s Planetary Defense Coordination Office continues to track near-Earth objects (NEOs), especially those like Bennu, which come within approx. 7.5 million kilometers (Earth’s orbit and classified as potentially dangerous objects. Between 2175 and 2199, the chance that Bennu will affect the Earth is only 1-in-2,700, but scientists will still not turn their backs on the asteroid. Bennu swims through the solar system on a path that scientists have confidently predicted, but they will refine their predictions by measuring the Yarkovsky effect at OSIRIS-REx and with future observations from astronomers.
8. Sampling of Bennu is getting tougher than we thought.
Early ground-based observations of the asteroid suggested that it had a smooth surface with a regolith (the top layer of loose, unconsolidated material) consisting of particles smaller than an inch (a few centimeters) in size – at most. When the OSIRIS-REx spacecraft was able to take higher resolution images, it became clear that sampling of Bennu would be far more dangerous than previously thought: new images of Bennu’s surface show that it is mostly covered. of massive stones, not small rocks. The OSIRIS-REx was designed to be navigated within an area of Bennu of almost 2,000 square meters (meters), approximately the size of a parking lot with 100 spaces. Now it has to maneuver to a safe place on Bennus’ rocky surface within a limit of less than 100 square meters, an area of about five parking spaces.
9. Bennu was named after an ancient Egyptian deity.
Bennu was named in 2013 by a nine-year-old North Carolina boy who won Name the asteroid! competition, a collaboration between the mission, the Planetary Society and the LINEAR asteroid survey that discovered Bennu. Michael Puzio won the competition by suggesting that the spacecraft’s Touch-and-Go Sample Mechanism (TAGSAM) arm and solar panels resemble neck and wings in illustrations by Bennu, which ancient Egyptians usually depicted as a gray heron. Bennu is the ancient Egyptian god associated with the sun, creation and rebirth – Puzio also noted that Bennu is the living symbol of Osiris. The myth of Bennu fits the asteroid itself, as it is a primitive object dating back to the creation of the solar system. Themes of origin and rebirth are part of the history of this asteroid. Birds and bird-like creatures are also symbolic of rebirth, creation and origin in various ancient myths.
10. Bennu still surprises us!
The spacecraft’s navigation camera observed that Bennu spit out streams of particles a few times each week. Bennu is apparently not only a rare active asteroid (only a handful of them have not yet been identified), but possibly with Ceres explored by NASA’s Dawn mission, among the first of its kind that humanity has observed from a spacecraft. Recently, the mission team discovered that sunlight can crack rocks on Bennu and that it has pieces of another asteroid scattered across the surface. Several pieces will be added to Bennus’ cosmic puzzle as the mission progresses, each bringing the evolutionary history of the solar system into sharper and sharper focus.
Goddard provides overall mission management, systems engineering and security and mission security for OSIRIS-REx. Dante Lauretta of the University of Arizona, Tucson, is a principal investigator, and the University of Arizona also leads the science team and mission planning and data processing science observation. Lockheed Martin Space in Denver built the spacecraft and provides aircraft operations. Goddard and KinetX Aerospace are responsible for navigating the OSIRIS-REx spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers Program, administered by NASA’s Marshall Space Flight Center in Huntsville, Alabama, for the Agency’s Directorate of Science Mission in Washington.